Re: Marshosaurus

["Jonathan R. Wagner" <znc14@ttacs1.ttu.edu>]

Nick Pharris wrote (about _Marshosaurus_):

>The pubis is long and slender, like that of _Sinraptor_ (Currie and Zhao,
>1993, pg. 2068).  It is also strongly bowed (concave down and back).  In this
>respect it is rather like the pubis of _Coelurus_ (_The Dinosauria_, pg.
>288).  _Siamotyrannus_, a probable sinraptorid, also shows a slight bowing of
>the pubis, but it is nowhere near as pronounced (Buffetaut et al., 1996, pg.
>690).
        And some ceratosaurs. On Sun, 23 Mar 1997, I noted:
"And the pubes [of _Indosuchus_] look somewhat like _Marshosaurus_..."

>The obturator notch in the pubis of _M. bicentesimus_ is rather more open
>(and _Allosaurus_-like) than in known sinraptorids.
        This could have something to do with ontogeny...

>The ischium compares very favorably to _Allosaurus_, having a triangular base
>and a prominent, proximally-placed obturator flange.  As in _Allosaurus_, the
>ischiadic rod is long, straight, slender, and flared distally.  In this
>respect it is rather more like the ischium of _Allosaurus_ than like those of
>sinraptorids, which are broader and bear a hook at the end.
        Of course, the pelves of the sinraptorids are highly variable,
having both primitive- and allosaur-like morphologies in the same clade.

>Theropod pelves are far more diagnostic than most people give them credit
>for!
        While I have been a big proponent of this in the past, every time I
compare pelvic morphology to phylogeny, I come up short. Possible
homoplaisy, ontogenetic variation, and potential mispolarization of
characters all lead me to *strongly* caution you against such beliefs. Look
at the case of _Yangchuanosaurus_ and _Sinraptor_. With only the pelves,
what would you say about them?
        On the other hand, I agree with you in this one case. Marsho seems
likely to be a carnosaur. Now, if you wanna wrangle, we can talk
_Stokesosaurus_, but check the archives first...

        Wagner
----------------------------------------------------------------------------
    Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
               "Not the One..." -- Zathras (not Zathras)